1. Field of the Invention
The invention pertains to the field of variable cam timing systems. More particularly, the invention pertains to a variable cam timing system including a phaser with concentric cams.
2. Description of Related Art
US Published Application No. US 2005/0279302 discloses a vane-type phaser driven by a crankshaft that drives the inner shaft and the outer tube of a first single cam phaser camshaft, which is coupled for rotation with the inner shaft and the outer tube of a second single cam phaser camshaft by drive links. The drive links are meshing gearwheels. The phaser may alter both the inner shafts and outer tubes of both camshafts or individual single vane-type phasers may each transmit torque to the first and second camshafts.
The first and second camshafts each have cams formed directly on the two inner shafts and other cams formed on the two outer tubes. Cams that rotate with the outer tubes have collars coupled to the outer tube by heat shrinking and cams that rotate with the inner shaft are loose fit on the outer tube and are connected to the inner shaft by pins that pass through the circumferentially elongated slots in the outer tube.
U.S. Pat. No. 7,036,473 discloses an adjustable camshaft with an elongated shaft which includes multiple shaft sections carrying intake and/or exhaust cam lobes. The first shaft section includes a shaft extending therefrom, and the second shaft section includes a hollow sleeve extending therefrom to accept the shaft therein to rotatably associate the first shaft section with the second shaft section. With the first and second shaft sections rotatably associated with each other, the sections may be selectively rotated relative to each other in order to adjust a displacement angle between the cam lobes to alter the intake and exhaust timing. The elongated shaft is attached to a drive/timing gear assembly which includes a gear and hub. An inner shaft may extend through the elongated shaft for attachment to the engine block. The cams may be locked to the shaft and relative to one another by a locking nut or a pin.